I use both Stanza and Calibre on my mac. Here's a few things off the top of my head in regards to viewing the files, converting them, and having the title/author appear correctly on your eReader

Stanza Desktop for mac
pros:
faster to load than the calibre viewer
exports a variety of files, which is great if you don't mind missing some TOC
Can send ePub files to Stanza on the iPhone/iPod Touch
reads a lot of different eBook file formats all in one app

cons:
Doesn't auto-gen a TOC if none is present
File conversion doesn't always set the metadata (like Title and Author) correctly.

duly noted neutrals for me:
Stanza flows the pages one after another kind of like Word's reading view.
no "send to device" button

Calibre for mac:

pros:
allows for content management including setting metadata
batch convert to one of the supported file types
can auto-generate a Table Of Contents if the file has the right tags or if you're familiar with Regular Expressions

cons:
batch convert is only to 3 file types.
No Find and Replace for batch editing of metadata
Need to set the title/author guessing to the correct format before you import especially if you have a lot of books or you'll be editing the titles for a while...

duly noted:
viewer is more like a browser viewer or Word's print layout view.

Thanks for the comparison there. Good job. I see as well that Calibre has some emphasis on being an e-book organizer for you computer as well. It's tag and meta-data functions are pretty handy. Looks like for me anyway, this journey into e-books will be requiring me to use a combination of both Stanza and Caliber. At least that will be easier since they're both free! And looking at their history, the products have both been evolving pretty rapidly.

Anyway, my intent wasn't to tell people to use one product over another so if it came across that way to anyone, I apologize. Just wanted to share another product I'd found that seems to work good and that I hadn't seen mentioned on the forum yet.

Anyway, my intent wasn't to tell people to use one product over another so if it came across that way to anyone, I apologize. Just wanted to share another product I'd found that seems to work good and that I hadn't seen mentioned on the forum yet.

Yup. I have both and use them both. Just wanted to mention a few things possibly useful to others. I'm always looking for a way to speed up the file conversion/viewing so I can get on with reading

Not sure if maybe this is addressed somewhere else, but I'm a new Kindle 2 user and trying to figure out Calibre. I've downloaded several free .prc books and am using Calibre to correct the meta info so it shows correctly on the Kindle. I've figure this part out, but seem to be losing the internal TOC links after I adjust the meta info and complete the conversion (from mobi to mobi). The TOC links show up, but when I click them (either in the built-in viewer or on the Kindle) that link just takes me back to the cover page. Is there a solution to this or maybe I'm just missing something?

Actually, if you load a .doc or .rtf (or whatever else Stanza can load), you can "Export Book" (File menu, next to the bottom) as one of seventeen different formats. Amazon Digital, Mobi, ePub are among them.